N165 Quiz 4

Dorsal stream in language

dorsal regions on the brain involved in speech production

Ventral stream in language

ventral regions of the brain involved in speech comprehension

The Hickok-Poeppel language model

A model of brain areas involved in language comprehension and speech production, describes dorsal pathway for production and ventral pathway for comprehension

Aphasia

“lack of speech” but not a result of deficit in sensory, intellectual, or psychiatric functioning, nor muscle weakness; deficit arises from damage to language-specific cortical regions; several types of aphasia exist

Broca’s aphasia

Aphasia characterized by slow, effortful speech output lacking function words, problems with grammar and articulation, in which patients rely on high-frequency content words. Patients have deficit in repetition, naming, and fluency, but can comprehend normally.

Wernicke’s aphasia

Aphasia characterized by fluent, meaningless speech with many semantic errors and little understanding (often with anosognosia). Patients have deficits in repetition, naming, comprehension, and have paraphasic fluency. Severe case: no concept of what language is for.

Paraphasia

Feature of aphasia where one loses the ability of speaking correctly, substitutes one word for another, and changes words and sentences in an inappropriate way. The patient’s speech is fluent but error-prone.

Word salad

Apparently fluent speech, but meaningless

Anosognosia

Deficit of self-awareness; a condition in which a person who suffers certain disability seems unaware of the existence of his or her disability

Arcuate fasciculus

The neural white matter pathway connecting Broca’s area and Wernicke’s areas

Conduction aphasia

Aphasia due to damage to the arcuate fasciculus resulting in poor repetition and naming, but normal comprehension and fluency

Transcortical sensory aphasia

Aphasia that is similar to Wernicke’s aphasia, except that patients are able to repeat language they heard (without understanding)

Transcortical motor aphasia

Aphasia associated with right hemiparesis (paralysis or inability to move) that is similar to Broca’s aphasia, except patients are able to repeat

Global aphasia

Associated with right hemiparesis, characterized by severe communication difficulties in both speech and comprehension; patients may have no concept of language as communication.

Transcortical mixed aphasia

Similar to global aphasia, but patients are able to repeat.

Anomic aphasia

Aphasia in which word-finding is severely impaired, usually from damage to parietal and/or temporal lobes, and patients resort to circumlocution.

Averbia

Specific aphasia in which patient loses ability to use verbs

Color anomia

Specific aphasia in which patient loses ability to use color words

Circumlocution

The use of other words to describe a specific word or idea which cannot be remembered

Pure word deafness

Inability to understand spoken language despite having normal hearing, reading, and writing abilities.

Amusia

Difficulty perceiving / producing music

Speech entrainment therapy

Patients practice mimicking audio-visual speech stimuli; enables them to produce fluent speech in real time

Subsystems of speech

1. respiration: processing of breathing

2. phonation: process by which the vocal folds produce certain sounds through quasi-periodic vibration

3. Resonance: prolongation of sound during speech

4. articulation: the movement of the tongue, lips, jaw, and other speech organs to make speech sounds

Dysarthria

Motor disorder affecting any or all of the 4 subsystems of speech

Spastic dysarthria

Motor disorder caused by damage to the upper motor neurons, which originate in motor region of cerebral cortex and carry motor information down to the lower motor neurons at a specific brain stem or spinal cord level

• causes: cerebral palsy, stroke, multiple sclerosis

• symptoms: harsh, strained voice; vocal pitch breaks; reduced speed of articulation

Flaccid dysarthria

Motor disorder caused by damage to lower motor neurons, which bring nerve impulses from upper motor neurons out to the muscles

• causes: brainstem stroke, cranial nerve palsy, myasthenia gravis (chronic autoimmune neuromuscular disorder that is characterized by fluctuating weakness of the voluntary muscle groups)

• symptoms: reduced lip closure and strength of articulatory; hyper-nasality, breathy voice

Speech apraxia

A developmental or acquired problem with speech production not associated with muscle weakness. Its symptoms include difficulty putting sounds and syllables together in the correct order to form words. May be developmental as in the verbal apraxia of childhood, or acquired.

Stuttering

Speech disorder where the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words or phrases, and involuntary silent pauses. May be caused by genetic mutations / head trauma.

• therapy: relaxation techniques, singing, and choral reading

Cluttering

Fluency disorder where the patient has a problem with rate, word confusion, and disorganized thoughts. Language is most clear at the start of utterances, but rate increases and intelligibility decreases towards the end. Patients are often not aware of the disorder, but can improve with therapy that focuses on attending to speech details.

Spoonerisms

Phonemic substitution

Malapropism

Wrong word substitution

Freudian slips

Error in speech from ‘unconscious mind’

Odorant molecule

Any substance capable of stimulating the sense of smell by binding to an olfactory receptor; substance must be volatile (able to vaporize)

Olfactory epithelium

AKA olfactory neuroepithelium, a sheet of cells that contains the olfactory receptors and lines the upper part of the nasal passages. It is covered by mucous layer where odorants must be absorbed before activating the olfactory receptors

Olfactory receptors

Expressed in dendrites of the olfactory receptor neurons and are responsible for detection of odorant molecules. Can bind to a range of odorant molecules with different degrees of activation. A single odorant molecule can bind to a number of olfactory receptors with varying affinities

Olfactory receptor neurons

Bipolar neurons with dendrites facing the nasal cavity (in the olfactory epithelium) and axons that pass through the openings in the cribriform plate (bone) to synapse in the olfactory bulb. Olfactory receptors are located along the dendrites and lie across the olfactory epithelium within the mucus layer. These neurons make up the ‘olfactory nerve’ and are one of the 3 structures in the brain that undergoes continuing neurogenesis in adult mammals.

Olfactory nerve

First carnival nerve (CN I), made of many small nerve fascicles of the olfactory receptor neurons. The olfactory nerve is unique among cranial nerves, because it is capable of some regeneration if damaged

Cribriform plate

A section of the bone that separates the nasal cavity from the brain. Contains many small holes through which the olfactory receptor neurons project axons.

Clinical significance:

i) fractured cribriform plate —> CSF leak into the nose and loss of sense of smell

ii) Tiny holes of cribriform plate becomes entry point for pathogenic amoeba (destroys olfactory bulb and adjacent inferior surface of the frontal lobe of the brain before spreading to rest of brain)

Trigeminal sense

Sensation of touch, pressure, pain, temperature in mouth, eye, nasal cavity that is carried by trigeminal nerve (CN V). ~70% of odorants co-activate both the olfactory nerve and trigeminal nerve.

Olfactory bulb

Multi-layered structure at ventral surface of brain that receives input from olfactory receptor neurons and sends output to cortex via mitral cell axons. The olfactory-receptor-neuron axons that form synapses in olfactory bulb glomeruli are also capable of regeneration following regrowth of an olfactory receptor neuron in the olfactory epithelium.

Olfactory glomerulus

Spherical structure located in the olfactory bulb where synapses form between axon terminals of the olfactory nerve and dendrites of mitral cells. Each glomerulus receives input from olfactory receptor neurons expressing only one type of olfactory receptor. The glomerular activation patterns within the olfactory bulb are thought to represent the odor being detected. Specifically, the glomeruli layer represents a spatial odor map organized by chemical structure of odorants.

Mitral cells

Neurons located in the olfactory bulb that receive inputs from olfactory receptor neurons within the glomeruli, along with inputs from modulatory cells, and then project axons to several cortical areas including the olfactory tubercle and piriform cortex and regions in the limbic system.

Olfactory tract

Bundle of axons including those from the mitral cells that connects the olfactory bulb to several target regions in the brain.

Olfactory tubercle and piriform cortex

Ventral regions together considered ‘primary’ olfactory cortex. Both regions are involved in identification of odor type and concentration.

• Olfactory information does not pass through thalamus before reaching these cortical regions.

Limbic system

Several interconnected regions in the medial temporal lobe that play important roles in processing emotion and memory.

1 of the functions: higher-order olfactory processing — tying order to emotion and memory

Sniffing

Key for olfactory perception: odor localization, odor identification and olfactory attention

Anosmia

Lack of ability to smell; associated with trauma to olfactory neurons projecting through the cribriform plate bone. Damage to one olfactory bulb can cause unilateral anosmia, which is only noticeable if nostrils are tested separately.

Hyposmia

Decreased ability to smell; often associated with clogged nasal sinuses or from nerve damage from trauma / infection

Dysosmia

Things smell differently than they should; often associated with hormonal changes like pregnancy, with clogged sinuses as seen in colds, or with nerve damage from trauma, infection.

Hyperosmia

Abnormally acute sense of smell, often associated with hormonal changes like pregnancy

Phantosmia

“hallucinated smell,” often unpleasant, commonly seen as an early symptom of a seizure in temporal lobe epilepsy.

Tastant molecule

Any substance capable of stimulating the sense of taste

Papillae

Raised protrusions of the tongue surface, where majority of the taste buds sit. 4 types of papillae present, differ by shape and location (within a papilla)

• Filiform papillae, Fungiform papillae, Foliate papillae, and Circumvallate papillae

Filiform papillae

Thin, long papillae “V”-shaped cones that don’t contain taste buds but are the most numerous. Mechanical, not involved in gustation.

Fungiform papillae

Slightly mushroom-shaped if looked at in section. Present mostly at tip of tongue and the sides

Foliate papillae

Ridges and grooves towards the posterior part of the tongue found on lateral margins

Circumvallate papillae

Only 3-14 of these papillae on most people, present at the back of the oral part of the tongue. Arranged in a circular-shaped row just in front of the sulcus terminalis of the tongue

Taste bud

Structure on the tongue that contains several taste receptor cells. A young tongue contains ~10,000 taste buds

Taste receptor cells

Provide taste information. Located throughout the tongue in the taste buds, have areas of higher sensitivity, and have a very short life span

Microvilli

Microscopic cellular membrane protrusioni that increase the surface area of cells and minimize any increase in volume and are involved in a wide variety of functions

Taste pore

Any of numerous spherical clusters of receptor cells found mainly in the epithelium of the tongue and constituting the end organs of the sense of taste

Supertasters

people who have a genetic mutation producing extra fungiform papillae and an increase of gustatory nerve fibers per papilla. They therefore experience a greater intensity of taste than normal, and may be espec

Gustatory nerves

Nerve fibers at each taste bud that receive information from the taste receptor cells. Their axons join three different cranial nerves to carry taste information to cortex.

Anterior insula & Frontal operculum

Adjacent cortical regions involved in taste processing; considered to be primary gustatory cortex. Plays a primary role in taste identification and evaluation of taste intensity

Orbitofrontal cortex for taste

Ventral region of the frontal lobes that is located just above the orbits of the eyes. Contains secondary gustatory cortex, which is involved in identifying taste, determining the reward value of a taste, combining multi sensory information to determine flavor, and signaling satiety (fullness).

Flavor

Multisensory experience, relies on integration of cues from most of the human senses. The process of flavor perception involves the complex interaction of taste with the smell, texture (from S1), and sight of food. Flavor perception changes over time during a meal to signal satiety

Gustatory map

cortical representation of the different taste modalities; recent research shows a gustatory map in the right insula

Disorders of taste

• ageusia, hypogeusia, dysgeusia

• causes: medication side effects, vitamin deficiencies, and respiratory illnesses with clogged nasal sinuses are common causes of dysgeusia and hypogeusia. Trauma is common cause

ageusia

complete loss of taste; patients will not be able to discriminate differences among sweetness, sources, bitterness, saltiness, and umami

Hypogeusia

partial loss of taste; taste sensitivity is reduced

Dysgeusia

Distortion or alteration of taste; food tastes abnormal

Disorders of the tongue

Geographical tongue, fissured tongue

Geographical tongue

Inflammatory condition of the mucous membrane of the tongue where the loss of fungiform papillae produce smooth, red, painful regions that change location over time; may result from other infections or medications like antibiotics

Fissured tongue

Benign condition characterized by deep grooves (fissures) in the top surface of the tongue; associated with geographical tongue, aging, environmental factors, and genetic conditions (Down’s syndrome).

Cross-modal perception

Occurs where perception involves interactions between two or more different sensory modalities

Synesthesia

A phenomenon where stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway; a type of cross-modal perception. May be associated with improved memory and faster reaction times on certain tasks

Causes of synesthesia

developmental: from differences in white matter connections, such as a decrease in synaptic pruning

Acquired: from sensory, drugs, or trauma

Projector synesthetes

Similar experience of synesthetic percepts in quality to real-world perceptions. Arises from changes earlier in sensory processing pathways

Associator synesthetes

Experience their synesthetic sensations within their internal mental space. For example, they would see the letters as appearing black/white, but automatically associate the letters with colors in their mind / memory. May arise from higher-order sensory regions, linking basic sensory perception with associated memory, emotion, or sensory mental imagery

Visual search task

More difficult to search for a different number if the same color. Grapheme-color synesthetes have a reaction time like there is a clear color difference when the numbers match their synesthetic perceptions.